Stereocontrolled synthesis of 22-hydroxy-23-acetylenic steroids, key intermediates in steroid side chain construction. Observation of a directive effect by an α-chiral site during asymmetric reduction with -B-3-pinanyl-9-BBN (Alpine-Borane)
作者:M.Mark Midland、Young C. Kwon
DOI:10.1016/s0040-4039(01)81738-x
日期:1984.1
An efficient stereoselective synthesis of 22-R- and 22-S-hydroxy-23-acetylenic steroids has been developed using R-Alpine-Borane (125:1, R:S) and L-Selectride (1:11, R:S) to reduce the 22-keto steroid. S-Alpine-Borane provides an unexpectedly low 1:2.7, R:S ratio due to the influence of the α- chiral center at C-20 of the steroid.